Auxin herbicides have proven to be effective and highly beneficial for control of unwanted plants. Auxin herbicides include 2,4-D (2,4-dichlorophenoxyacetic acid), 2,4-DB (4-(2,4-dichlorophenoxy)butanoic acid), dichloroprop (2-(2,4-dichlorophenoxy)propanoic acid), MCPA ((4-chloro-2-methylphenoxy)acetic acid), MCPB (4-(4-chloro-2-methylphenoxy)butanoic acid), aminopyralid (4-amino-3,6-dichloro-2-pyridinecarboxylic acid), clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), fluroxypyr ([(4-amino-3,5-dichloro-6-fluoro-2-pyridinyl)oxy]acetic acid), triclopyr ([(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid), diclopyr, mecoprop (2-(4-chloro-2-methylphenoxy)propanoic acid) and mecoprop-P, dicamba (3,6-dichloro-2-methoxybenzoic acid), picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), quinclorac (3,7-dichloro-8-quinolinecarboxylic acid), aminocyclopyrachlor (6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid), agriculturally acceptable salts of any of these herbicides, racemic mixtures and resolved isomers thereof, and mixtures thereof. Dicamba has proven to be a particularly effective auxin herbicide and is typically formulated as the sodium, dimethylamine, isopropylamine or diglycolamine salt.
One problem associated with auxin herbicides is loss of their herbicidal efficacy through dilution in ground water. In particular, this problem involves leaching of the auxin herbicide by ground water into lower soil layers. Auxin herbicides act in controlling unwanted plants by passing through the roots or stem of the plants. Accordingly, leaching of the herbicide into the lower soil layers reduces herbicidal efficacy. In addition, one benefit of auxin herbicides generally is providing efficacy over a relatively long period of time. Auxin herbicidal formulations are known as having a relatively high residual effect. However, dilution in ground water and leaching of the auxin herbicide into lower soil layers undermines the residual effect of auxin herbicide formulations. Thus, a need exists for an auxin herbicide formulation that avoids the problem of leaching and provides a relatively high residual effect.
Off-site movement is also often associated with dicamba and other auxin herbicides. Under certain conditions of application, dicamba can migrate from the application site to adjacent crop plants, such as soybeans and cotton, where contact damage to sensitive plants can occur. An additional need exists for auxin herbicide formulations that provide reduced off-site movement.
A further need exists for an auxin herbicide formulation that is suitable for use in connection with other herbicides (e.g., glyphosate) along with the auxin herbicide that also addresses the above-noted issues.